This invention relates to optical fibers, and, more particularly, to the splicing of two optical fibers to form a single spliced length of fiber.
Optical fibers are strands of glass fiber processed so that light beams transmitted therethrough are subject to total internal reflection. A large fraction of the incident intensity of light directed into the fiber is received at the other end of the fiber, even though the fiber may be hundreds or thousands of meters long. Optical fibers have shown great promise in communications applications, because a high density of information may be carried along the fiber and because the quality of the signal is less than subject to external interferences of various types than are electrical signals carried on metallic wires. Moreover, the glass fibers are light in weight and made from a highly plentiful substance, silicon dioxide.
Glass fibers are typically fabricated by preparing a cylindrical preform of glasses of two different optical indices of refraction, with a core of one glass inside a casing of a glass of slightly lower refractive index, and then processing the preform to a fiber by drawing or extruding. The optical fiber is then coated with a polymer layer termed a buffer to protect the glass from scratching or other damage. The optical fibers and the buffers may be made with varying dimensions, depending upon their intended use and the manufacturer. As an example of the dimensions, in one configuration the diameter of the glass optical fiber is about 0.005 inches, and the diameter of the fiber plus the buffer layer is about 0.010 inches.
For most applications of optical fibers, it is necessary to be able to splice lengths of two separate optical fibers together to form a single spliced length of optical fiber. The need to splice optical fibers together typically arises when it is necessary to use a length longer than can be made from a single preform, when an existing length of fiber breaks, or when apparatus such as an amplifier is to be incorporated into a length of fiber.
The optical fiber splice must be accomplished so that there is no significant increase in loss of light in the vicinity of the splice, and the spliced fiber has a sufficiently high strength to withstand handling in normal operations such as winding under tension onto a bobbin, or unwinding from the bobbin. Additionally, it must be possible to restore the buffer layer initially on the fibers being spliced, if any.
There have been proposed techniques for splicing optical fibers. In general, these techniques have proved unsatisfactory because of mechanical weakness in the region of the splice that leads to preferential failure near the splice in later service, and the use of cumbersome equipment and noxious chemicals in the splicing operation.
There therefore exists a need for an improved method for splicing optical fibers together, and such spliced fibers. The improved technique should exhibit low light loss and high strength of the spliced region, and have the ability to provide a continuous buffer coating over the spliced region. The splicing method should be amenable to accomplishing large numbers of splices in a safe manner. The present invention fulfills this need, and further provides related advantages.